A service gateway (SGW) is a relay apparatus which connects communication networks with different protocols. The relay apparatus connects, for example, a local area network (LAN) and a wide area network (WAN) and relays packets received from the LAN or the WAN to the network including a destination device of the packets.
The LAN is a network which is installed in, for example, a corporate office. In contrast, the WAN can be installed in an Internet environment. The relay apparatus is used to enable a device in the LAN to perform data communication through the Internet. In a corporate network, security, such as a firewall for preventing an unauthorized access from the outside, is set. The setting of the firewall makes it possible to prevent the unauthorized access from the outside.
A related technique disclosed in, for example, JP 11-225154 A has been known. In this technique, when an unauthorized access has been initiated from the WAN, a relay apparatus disconnects the communication line directed to the WAN to improve security.
However, Japanese Laid-open Patent Publication No. 11-225154 merely discloses the technique to improve security and fails to disclose, for example, a technique to relay communication based on various types of protocols.